Multi-stage hydrocracking process



March 29, 1966 H. F. MASON ET AL 3,243,367

MULTI-STAGE HYDROCRAGKING PROCESS Filed Nov. 26, 1963 FEED 19 GAS H2 ssor-" PRODUCTS 6 O c -sso F 55o 650 F s g as 25 [0 U 2 I6 3 o 20 o [I D. l 5' u. 2

o 650 F noo F 27 INVENTORS HAROLD F. MASON BEN G. BRA) United States Patent O 3,243,367 MULTiI-STAGE HYDRQCRAQKING PRBCESS Harold F. Mason, Berkeley, and Ben G. Bray, El Cerrito,

Califi, assignors to Chevron Research Company, a corporati'on of Delaware Filed Nov. 26, 1963, Ser. No. 325,949 5 Claims. (Cl. 208-59) This invention relates to a hydrocarbon conversion process, more particularly to a hydrocarbon conversion process for'converting petroleum distillate and residuum feeds into various valuable products, and still more particularly to a catalyticconversion process capable of producing middle distillates and gasoline from said feeds.

It is well known that nitrogen in a hydrocarbon feed is deleterious to certain hydrocracking catalysts, particularlyvhig-hly acidic hydrocracking catalysts, and that in order to provide a practical process for producing gasoline over a highly acidic hydrocracking catalyst from a feed containing substantial amounts of nitrogen, it is generally necessary to first hydrofine' the feed to remove substantially alL-of the nitrogen. It is also well known that such highly acidic catalysts do not result in the productionof-'susbtantialquantities of middle distillates and that where gasoline'production and also substantial middle distillate" production is desired a catalyst having no more than weak acidity is desirable. While it is possible to meet the aforesaid problems by operating a two-stage process wherein the hydrofining-hydrocr-acking catalyst having no more than weak acidity is used in the first stage and an acidic hydrocracking catalyst is used in? the second stage, such a process still has undesirable aspects. Operation of 'the'first stage at hydrofining conditions severe enough to reduce the nitrogen content of thefeed to an acceptably low level frequently results in a greater amount of hydrocracking, light gas production and catalyst fouling inthe first stage than is desired. On the other hand, operation of the first stage at less severe conditions which do not result in an excessive amount ofhydrocracking frequentlyleaves a greater concentration of nitrogen in the effluent from the first stage than can be tolerated for sustained periods by the acidic catalysts in the second stage.

In view of the foregoing, it 'is an object of the present invention to provide a multi-stage process for coverting nitrogen-containing feeds to gasoline and middle distil-.

lates wherein said feeds. are hydrocracked and partially hydrofined with catalysts having no more than weak acidity to produce middle distillate products and higher boiling materials and wherein selected portions of said higher boiling materials are hydrocracked in a sub sequent'stage in the presence of a more acidic catalyst, and wherein it is not necessary to remove substantially all of the nitrogen from said feeds with said catalysts having no more than weak acidity in order to produce a feed for said subsequent stage having an adequately low nitrogen content.

The invention will best be understood, and further objects and advantages thereof will be apparent, from the following description when read in conjunction with the accompanying drawing which is a diagrammatic illustration of process units and flow paths suitable for carrying out the process of the present invention.

In accordance With one embodiment of the present invention there is provided a process for producing gasoline and middle distillates from a hydrocarbon feed selected from the group consisting of nitrogen-containing petroleum distillates and petroleum residua boiling above 650 R, which comprises selecting at least two feed fractions having different boiling ranges, separately hydrocracking each of said fractions in the presence of from 1,000 to 10,000 s.c.f. of hydrogen per barrel thereof in a conversion zone at a temperature from 500 to 950 F., a pressure above 500 p.s.i.g., a per-pass conversion above 40%, and an LHSV of 0.1 to 4.0 With a catalyst having no more than weak acidity comprising at least one hydrogenating component selected from the Group VI metals and compounds of Group. VI metals and at least one hydrogenating component selected from the Group VIII metals and compounds of Group VIII metals in intimate association with a silica-containing support, recovering at least one product boiling. below. 550 F. from said zone, and separately hydrocracking that. portion of the efiluent from said zone boiling above 550 F.

and below the initial boiling point of the feed to said zone to produce additional products boiling below In accordance with a more specific embodiment of the present invention, there is provided a process for producing gasoline and middle distillates from a hydrocarbon feed selected from the group consisting of nitrogencontaining petroleum distillates and petroleum residua, boiling above 650 F. which comprises separating said:

feed into a first-fraction and a second fraction of different boiling range, hydrocracking said first fraction in the presence of from 1000 to10,000 s.c.f. of hydrogen per barrel thereof in a first conversion zone at a temperature of from 500 to 950 F., a pressure above 500 p.s.i.g., a per-pass conversion above 40%, and an LHSV. of from 0.1 to 4.0with a catalyst having no more than weakacidity comprising at least one hydrogenating component selected from the Group VI metals and compounds of Group VI metals and at least one hydrogenating com-- ponent selected from the Group VIII metals and compounds of Group VIII metals in intimate association with? a silica-containing support, recovering at least one product boiling below 550 -F. from said first conversion zone,- hydrocracking'said second fraction in-thepresence of from 1000 to 10,000 s.c.f. of hydrogen per barrel thereof in:

a second conversion zone at a temperature of from 500 to 950 F., a pressureabove' 500'p.s.i.g., a per-pass con-: version above 40%, and an LHSV of from-0.1 to 4.0

with a catalyst having-no more thanweak acidity comprising at least one hydrogenating component selected from the Group VI metals and compounds of Group VI metals and at least one hydrogenating component selected from the Group VIII metals and compounds of. Group VIII metals. in intimate associationwith a silica-containing support, recovering at least one product boiling below 550 F. from said second conversion zone, passing to a third conversion zonev from said first conversion zone a fraction boiling above 550 F. and below the initial boiling point of the feed to said first conversion zone, passing to said third conversion zone a fraction boiling above 550 F. and below the initial boiling point of the feed to said second conversion zone, and hydrocracking in said third conversion zone at a per-pass conversion above 40%, said fractions passed thereto to produce additional products boiling below 550 F.

Suitable feeds for use in the process of the present invention are nitrogen-containing petroleum distillates and nitrogen-containing petroleum residua from which fractions can be selected boiling above 650 F., preferably fractions boiling between 650 F. and 1200 F., and mixtures of the foregoing. Heavy gas oils and catalytic cycle oils are excellent feeds to the process, as well as conventional FCC feeds and portions thereof. Residual feeds may include Minas and other parafiinic-type residua as Well as solvent decarbonized oils from a wide range of residua.

The aforesaid catalysts having no more than weak acidity comprise at least one hydrogenating component selected from the Group VI metals and compounds of the Group VI metals and at least one hy- Patented Mar. 29, 1966 drogenating component selected from the Group VIII metals and compounds of Group VIII metals. Preferred combinations of hydrogenating components include nickel sulfide and tungsten sulfide, nickel sulfide and molybdenum sulfide, and palladium sulfide'and molybdenum sulfide.

' The aforesaid catalysts having no more than weak acidity comprise a support, preferably one that is moderately acidic, but not more than moderately acidic, as compared with highly acidic supports such as silicaalumina. Said support preferably is selected from the group consisting of silica-magnesia supports, silica-alumina supports containing less than 70 weight percent of silica, and silica-alumina-magnesia supports having a silica content less than.80 weight percent.

. The aforesaid catalysts having no more than weak acidity are relatively nitrogen-insensitive compared with conventional acidic hydrocracking catalysts such as nickel sulfide on silica-alumina. Accordingly, the nitrogen content of the nitrogen-containing feed used in the process of the present invention may be relatively high and excellent hydrocracking results still may be obtained in the conversion zones containing said catalysts at reasonable temperatures without the necessity for rapidly raising the temperature to maintain conversion as is necessary when hydrocracking a high nitrogen content feed of a conventional acidic hydrocracking catalyst, such as nickel sulfide on silica-alumina. The nitrogen content of the feed in the present process may range from parts per million to 5000 parts per million. The process is especially attractive for processing heavy feeds containing at least 500 parts per million nitrogen.

- Although high nitrogen content feeds can be tolerated by said catalysts having no more than weak acidity, it will be noted that said catalysts also are excellent hydrodenitrification catalysts and are efficient in concurrently hydrofining as well as in hydrocracking the feed. Nevertheless, the process of the present invention may be rendered even more efficient if very high nitrogen content feeds are first hydrofined by conventional methods to at least somewhat reduce their nitrogen content before hydrocracking them in the presence of said catalysts having no more than weak acidity: in accordance with the present invention.

Conversion zones in the process of the present invention containing said catalysts having no more than weak acidity are operated at combinations of conditions selected from within the following ranges that will produce the desired degree of hydrocracking: a temperature of about 500 to 950 F., preferably 650 to 850 F.; a hydrogen partial pressure of 500 to 3500 p.s.i.g., preferably 1000 to 2500 p.s.i.g.; and an LHSV of from about 0.1 to 4.0, preferably 0.4 to 2.0. The hydrogen flow to said conversion zones may be from 1000 to 12,000 s.c.f. per barrel of feed, and preferably 2500 to 8000 s.c.f. per barrel of feed. The higher hydrogen partial pressures, particularly with unrefined feeds, give lower catalyst fouling rates, and therefore, for longer catalyst lives, it is preferable to operate above 2000 p.s.i.g. total pressure and above 1000 p.s.i.g. to hydrogen partial pressure.

A separate conversion zone may be used containing said catalyst having no more than weak acidity for each feed fraction of different boiling range that is to be processed, or, if desired, a single such conversion zone may be used to process each of said feed fractions alternately.

, The catalyst in the conversion zone subsequent to the conversion zones containing catalysts having no more than weak acidity may be any conventional active acidic hydrocracking catalyst, "for example nickel sulfide on silica-alumina, platinum on silica-alumina, cobalt sulfide on silica-alumina, various conventional fluoridedacidic hydrocracking catalysts, etc.

' ture of from 550 to 850 F. Generally, at least 3000 s.c.f. of hydrogen per barrel of feed will be supplied to said subsequent conversion zone, wherein normally from about 1000 to 2000 s.c.f. of hydrogen are consumed in the hydrocracking reaction per barrel of feed converted to synthetic products.

It is well known that nitrogen has an extremely deleterious effect upon the hydrocracking performance of acidic hydrocracking catalysts such as those used in said subsequent zone in the present process. It is well known that as the nitrogen content of the feed to a hydrocracking zone containing an acidic hydrocracking catalyst increases, the reaction temperature' must be raised if desired conversion levels are to be maintained. It is also well known that if the temperature must be raised beyond a certain point, for example 850 F., side reactions and nonhydrocracking reactions occur to win tolerable extent. Accordingly, it is well known that the nitrogen content of the feed to a hydrocracking zone containing an acidic hydrocracking catalyst should be kept below about 50 parts per million, preferably below about 10 parts per million, and still more preferably below about 2 parts per million. It is apparent that in a multistage process of the type with which the present invention is concerned, namely one in which a hydrofininghydrocracking catalyst of not more than moderate acidity is used in a first stage and a highly acidic hydrocracking catalyst is used in subsequent stage, the first stage must be operated at severe enough hydrofining conditions'to reduce the nitrogen content of the feed to the subsequent stage to an acceptable level. It is also apparent that there are frequent cases when such severe conditions in the first stage will result in an undesirably high level of hydrocracking in that stage. Heretofore, the operator of such a process faced a dilemma; if the first stage were operated at sufficiently mild hydrocracking conditions, insufficient hydrofining would be accomplished to reduce the nitrogen content of the feed to the subsequent stage to a tolerably low level.

' Heretofore it has been thought that the nitrogen concentration in the effluent from the first stage of the aforesaid type of process has been distributed relatively uniformly through said efiluent, and that if said effluent were fractionated, nitrogen would appear in the various fractions in approximately the same concentration. Very unexpectedly, it has now been discovered that this is not so, but rather that the nitrogen concentration in the synthetic portion of the efiluent, namely that portion boiling below the initial boiling point of the feed, is very substantially lower than the nitrogen concentration in that portion of the efiluent boiling within the feed boiling range. This surprising discovery has far-reaching consequences in the operation of a multi-stage process of the aforesaid type. In accordance with the present invention, it is now possible to operate a plurality of first stages, each containing a catalyst having no more than Weak acidity, at adequately mild hydrocracking conditions and permit the efiluent from each of said stages to contain a much higher total nitrogen content than was heretofore possible. This is accomplished by processing in the subsequent stage containing a highly acidic catalyst only those materials in the efiluent from each first stage that boil below the initial boiling point of the feed to that first stage. These materials, termed synthetic materials because they do not contain any materials boiling within the boiling range of the original feed to the stage in which they are produced, contain a very low concentration of nitrogen despite the fact that the higher boiling materials have a substantially higher nitrogen concentration. This may be illustrated by the following examplesz Example 2 A ;-750 ;t o about 1300 F. boiling range petroleum disljtillate containing 5475 parts per'million nitrogen is'distilled'int o twoequal fractions, boiling above and below about 950 F., respectively. Each fraction-is separately hydrocracked over a nickel sulfide-tungsten sulfide on silica-magnesia catalystunder conditions within the afore- .said. first conversion zone ranges and at a per-pass conversionof '50 percent. In hydrocracking the fraction boiling from 750 to about 950 F., a synthetic product .boiling from 500 ,to 700 F. is obtained and remaining higher boiling materials boiling above 700 F. are recycled. The500 to 700 F. product had a nitrogen content of 0.12 part per million. In hydrocracking the fraction boiling above about 950 F. a synthetic product boiling betweenv500 and,.950 F. is obtained and remaining higher boiling materials were recycled. The product boiling within the range'of 500 to 950 F. has a nitrogen content of 5.1 parts ,per million. Upon blending the products; obtained in the aforesaid separate hydrocracking operations theresulting product'blend boiling within the range 400 to 950 F. have a nitrogen content of 2.6 parts per million.

Referring now to the drawing, there shown is an exemplary diagrammatic illustration of an embodiment of process units and flow paths suitable for carrying out the process of the present invention.

A hydrocarbon feed which may be, and in this example is, a petroleum distillate feed containing materials boiling above 650 F., is passed through line 1 to distillation column 2, where it is separated into various fractions as shown. A gaseous fraction is removed from column 2 through line 3, a C 650 F. fraction is removed through line 4, and, if desired, a residuum fraction boiling above 1100 F. is removed through line 5. A 650 to 900 F. fraction is passed from separation zone 2 through line 6 into contact in hydrocracking zone 7 with the aforesaid hydrocracking catalyst having no more than weak acidity and with hydrogen entering zone 7 through line 8 under the hydrocracking conditions previously discussed, at a per-pass conversion preferably above about 40%. From zone 7, an efiluent is passed through line 9 to separation zone 10, from which hydrogen is recycled through line 15, ammonia is withdrawn through line 16, and remaining materials are passed through line 17 to separation zone 18. From separation zone 18 a product stream boiling below about 550 F., for example including gasoline and jet fuel components, is withdrawn through line 19. From separation zone 18, materials boiling above about 650 F., i.e., materials boiling within the range of the feed entering zone 7 through line 6, are returned to zone 7 through line 20. If desired a portion of the materials in line 20 may be passed to a catalytic cracking zone, or used for any other desired purpose, for example as a lube oil stock. From separation zone 18 a fraction boiling from about 550 to 650 F., i.e., approximately above the jet fuel boiling range and below the initial boiling point of the feed to zone 7, is passed through line 25 into contact in hydrocracking zone 26 with the aforesaid highly acidic hydrocracking catalyst and with hydrogen entering zone 26 through line 27, at a per-pass conversion preferably above about 40%.

A 900 to 1100 F. fraction is passed from. separation zone 2 through line 30 into contact in hydrocrackingzone 31 with the aforesaid hydrocracking catalyst having no more than weak acidity and with hydrogen entering zone 31 through line 32 under the hydrocracking conditions previously discussed, at a per-pass conversion preferably above about 40%. From zone 31 an eflluent is passed through line 33 to separation zone 34 from whichhydrogen is recycled through line 35 to zone 31 ammonia is withdrawn through line 36, and remaining materials are passed through line 37ito sepa-rationzone 3 8. From separation zone 38, pro'ducts boiling below about'550 F., includinggasol'ine and jet fuel components, are recovered through lines 39 and 19, and materials boiling above about 900 F., i.e., within the boiling rangeaof the feed entering zone 31 through line 30, are returned tolzone 31 through line 40. Aiportion of the materia-lsin line 40 may be passed through line 45 to a catalytic cracking zone, or used for any other desired purpose, for example as a lube stock. From separation'zone 38 a fraction boiling between about 550 and 900 F., i.e., approximately above the jet fuel boiling range and below the initialboiling point of the feed entering zone 31 through line 39, is passed through line 46 int-o contact in hydrocarcking zone 26 with the aforesaid highly acidicliydrocracking catalyst and with hydrogen entering zone 26 throughline 27 under the hydroc-racking conditions previously discussed, at aper-pass conversion above about 40%. The hydrocrackate effluent from zone 26 is passed through line 47 to separation zone 38 for separationintoproducts boiling below about 550 R, which arepassed through line 39, and materials boiling above about 550 R, which are returned to zone 26 through line 46 forfu-rther processing.

The nitrogen concentration in the stream passed through line 25 to conversion zone 26 is substantially lower than the nitrogen concentration in the stream returned through line 20 to conversion zone 7. The nitrogen concentration in the stream passed through line 46 to conversion zone 26 is substantially lower than the nitrogen concentration in the stream returned through line 40 to conversion zone 31.

From the foregoing, it will be seen that the process of the present invention is effective in producing both middle distillates, in particular jet fuels, and gasoline in varying ratios from heavy, nitrogen-containing feed stocks. It will also be seen that the process embodies a discovery which permits the production in the zones containing catalysts having no more than Weak acidity under surprisingly mild hydrofining conditions of fractions having adequately low nitrogen contents to be suitable feed stocks for the subsequent conversion Zone containing a catalyst having a high acidity.

Although only specific embodiments of the present invention have been described, numerous variations can be made of those embodiments without departing from the spirit of the invention, and all such variations that fall within the scope of the appended claims are intended to be embraced thereby.

We claim:

1. A process for producing gasoline and middle distillates from a hydrocarbon feed selected from the group consisting of nitrogen-containing petroleum distillates and petroleum residua boiling above 650 R, which comprises selecting at least two feed fractions having different boiling ranges, separately hydrocracking at a per-pass conversion above 40% each of said fractions in the presence of from 1000 to 12,000 s.c.f. of hydrogen per barrel thereof in a conversion zone at a temperature from 500 to 950 F., a pressure above 500 p.s.i.g. and an LHSV of from 0.1 to 4.0 with a catalyst having no more than weak acidity comprising at least one hydrogenating component selected from the Group VI metals and compounds of Group VI meta-ls and at least one hydrogenating component selected from the Group VIII metals and compounds of Group VIII metals in intimate association with a silica-containing support, recovering at least one product boiling below 550 F. from said zone, and separately hydrocracking at a per-pass conversion above 40% that portion of the efiluent from said zone boiling above 550 F. and below the initial boiling point of the feed to said zone to produce additional products boiling below 550 F.

2. A process for producing gasoline and middle distillates from a hydrocarbon feed selected from the group consisting of nitrogen-containing petroleum d-istillates and petroleum residua boiling above 650 R, which comprises separating said feed into afirst fraction and a second fraction of d'ifierent boiling range, hydrocrack-ing said first fraction inthe presence-of from 1000 to 12,000 s.c'.f. of hydrogen per barrel thereof in a first conversion zone at a temperature from 500 to 950 F., a pressure above 500 p.s.i.g., a per-pass conversion above 40%, and an LHSV of from 0.1 to 4.0 with a catalyst having no more than weak acidity comprising at least one hydrogenating component selected from the Group VI metals and compounds of Group VI metals and'at least one hydrogenating component selected from the Group VIII metals and compounds of Group VIII metals in intimate association with asilica-containing support, recovering at least one product boiling below 550 F. from'said first conversion zone, hydrocracking said second fraction in the presence of from 1 000 to 12,000 s.c.f. of hydrogen per barrel'the-reof in a second conversion zone at a temperature from 500 to 950 F., a pressure above 500 -p.s.i.g., aper-p'ass conversion'ab-ove 40%, and an LHSV a silica-containing support, recovering at least one product boiling below 550 F. from said second conversion zone, passing to a third conversion zone from said first zone a fraction boiling above 550 F. and below the initial boiling point of the feed to said first conversion zone, passing to said third conversion zone a fraction boiling above 550 F. and below the initial boiling point of the feed to said second conversion zone, and hyd-rocra-ckingin said third conversion zone at a per-pass conversion above said fractions passed thereto to produce additional products boiling below 550 F. .i I. 3. A process as in claim 2 wherein said third conversion zone contains a hydrocracking catalyst comprising at least one hydrogenating component in intimate association with an active, acid support, and wherein said third conversion zone is operated at a temperature from 500 to 950 F., a pressure above 500 p'.s.i.g'. and an LHSV of 0.1 to 4.0. r 4. A process as in claim 2 whereina fraction' boiling within the boiling range of the feed to said first conversion zone is recycled to said first conversion zone from the efliuent thereof. I

5. A process as in claim 2.Whe-rein a fraction boiling within the boiling range of the feed to said second conversion zone :is recycled tosaid second conversion zone from the eflluent thereof.

References Cited by the Examiner UNITED STATES PATENTS 3,026,260 3/1962 Watkins 26 68 3,159,568 12/1964 Priceet a1. 2os 111 3,175,966 3/1965 Burch 208 79 

1. A PROCESS FOR PRODUCING GASOLINE AND MIDDLE DISTILLATES FROM A HYDROCARBON FEED SELECTED FROM THE GROUP CONSISTING OF NITROGEN-CONTAINING PETROLEUM DISTILLATES AND PETROLEUM RESIDUA BOILING ABOVE 650*F., WHICH COMPRISES SELECTING AT LEAST TWO FEED FRACTIONS HAVING DIFFEREENT BOILING RANGES, SEPARATELY HYDROCRACKING AT A PER-PASS CONVERSION ABOVE 40% EACH OF SAID FRACTIONS IN THE PRESENCE OF FROM 1000 TO 12000 S.C.F. OF HYDROGEN PER BARREL THEREOF IN A CONVERSION ZONE AT A TEMPERATURE FROM 500* TO 950*F., A PRESSURE ABOVE 500 P.S.I.G. AND AN LHSV OF FROM 0.1 TO 4.0 WITH A CATALYST HAVING NO MORE THAN WEAK ACIDITY COMPRISING AT LEAST ONE HYDROGENATING COMPONENT SELECTED FROM THE GROUP VI METALS AND COMPOUNDS OF GROUP VI METALS AND AT LEAST ONE HYDROGENATING COMPONENT SELECTED FROM THE GROUP VIII METALS AND COMPOUNDS OF GROUP VIII METALS IN INTIMATE ASSOCIATION WITH A SILICA-CONTAINING SUPPORT, RECOVERING AT LEAST ONE PRODUCT BOILING BELOW 550*F. FROM SAID ZONE, AND SEPARATELY HYDROCRACKING AT A PER-PASS CONVERSION ABOVE 40% THAT PORTION OF THE EFFLUENT FROM SAID ZONE BOILING ABOVE 550*F. AND BELOW THE INITIAL BOILING POINT OF THE FEED TO SAID ZONE TO PRODUCE ADDITIONAL PRODUCTS BOILING BELOW 550*F. 